I wish to make a smooth motion like hips of belly dance
Note 1: It's not bad to have a lot of keyframes! You can easily get used to a key on every frame and grabbing large blocks of keyed animation. When animating over motion-captured or simulated data this is a common occurence. The graph editor should be intuitive, but not clean/tidy!
Note 2: A belly dancer's hips would likely move in an ∞ like shape or an ellipsoid, not in a circle (a very unnatural shape for movement).


A simple sin and cos function can be overlayed if the circular motion is happening on 2 axes only. Select the graphs, add a modifier each (sin and cosine), choose additive for both and set their phase multiplier to the same value. (You can type 1/pi in the phase multiplier field.)

If you want the movement on certain frames use the Restrict Frame Range functionality of the modifiers or keyframe the Influence.
When you want to edit the movement further you'll have to bake the action.
Another method is simply setting good keyframes and using interpolation to your advantage. Keying the four position (1, 0), (0, -1), (-1, 0) and (0, 1) gives us this awkward motion.

To fix this, make the extremes the start and end of the cycle and remove the breakdowns of the curve. Or rotation the Auto Clamped keys which prevent a smooth movement.